The present invention is directed to a blank stacking and turning device which is to be added to the outlet of a so-called printing/cutting machine producing packaging boxes.
U.S. Pat. No. 4,367,997, whose disclosure is incorporated herein by reference thereto and which claims priority from the Swiss Application which issued as Swiss Patent 633 761, discloses a device for piling blanks coming out of a printing/cutting machine in the form of three parallel streams, which are carried by a belt conveyor. Each of the streams is built up into a separate stack or pile. At the horizontal end of the conveyor, the blanks drop one by one into a table-shaped storage device, which is movable vertical in such a way as to keep the upper surface of the three side-by-side stacks at a constant height. Appropriate means are provided to stop the blank supply each time the expected pile height is obtained.
Once the pile height is obtained, the table is lowered to the level of a second crosswise conveyor extending perpendicular to the first conveyor and a pusher simultaneously shifts the three piles onto the second conveyor. The pusher is then moved backward, whereupon the table is set back to its initial height, at which piling or stacking is resumed. The build-up of new piles may then begin, while the three previously-formed piles or stacks are transferred crosswise one-by-one onto a second table on which the piles are shifted in a direction parallel to the first conveyor.
However, in view of the present steadily-increasing production speeds rising to, say, 3,000 boxes per minute, the time for forming a pile of approximately 250 box blanks per pile is approximately 5 seconds for each of the three streams. It is quite obvious that there is no possibility to proceed to consecutively shift both the table and the pusher in a sufficiently short period of time, which is still compatible with such production speeds. Moreover, since, for the future handling of the piles, for instance palletizing, the sides of these piles formed by the edges of the blanks are to be properly aligned or adjusted, these piles will have to be effectively rotated through 90.degree. during a transfer movement from the second to the third conveyor so that they will rest on the edges of the blanks forming the pile, thereby assuring the alignment or adjustment. The alignment of the other edges perpendicular to the first edges is achieved by means of joggers fitted on bars used for properly arranging the piles on the second table. The piles will then be collected either manually or automatically from the third table consisting essentially of belts, for instance, with a view toward palletizing.
However, such a device for aligning the pile sides has the following drawbacks. With high production speeds, it is difficult to obtain a crosswise shifting and subsequent 90.degree. rotation of the three piles successively in the course of the period of 5 seconds; it significantly increases the lengthwise encumbering of the machine; and, at the end of the alignment, the piles rest with the blank edges on a table which requires another pile rotation through 90.degree. to a second position so as to turn the printed side of the blanks downward. This second position corresponds to the one necessary for the subsequent infeed of the blanks into a so-called folding box gluing machine and, thus, to the one for their palletization.
For feeding the folding box gluing machine, a known method consists of putting previously-prepared piles into a turning device which enables turning the piles through 180.degree. so that a pile which was formed with the print facing upward can then be turned so that the print is facing downward. However, these have the sole purpose of turning and not stacking or aligning of the blanks in the piles.